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Speech sciences deal with the acoustical characteristics of speech by means of sophisticated soft wares as well as hard wares. Although, a speech science is a well known science in the developed countries, especially the western societies, however, it has been remained almost unknown in Iran, though, in recent years a group of scholars have been involved in this branch of science. The application of the speech sciences in the field of 'Speech and Language Therapy' has been widely accepted throughout the world. The main focus of these applications is the therapeutic aspects of the program, which is used for both adults and children. However, the non-therapeutic applications are mainly used for research purposes only. In this article, a brief introduction about the nature as well as the application of speech analysis for both normal and abnormal speeches is given. In addition, examples of the acoustical characteristics fconsonants and vowels such as, voice onset time (VOT), formant frequencies and spectrograms will be presented.